The production of ammonia by the synthesis of hydrogen and nitrogen at high pressure is old in the art. Existing processes provide for mixing hydrogen and nitrogen gas, raising the mixture to a high pressure by means of a main compressor sometimes referred to as a "make-up compressor" or a "synthesis gas compressor" and introducing such a mixture into a high pressure reactor where, usually with the aid of a suitable catalyst, the synthesis is initiated. Provision is usually made for recycling the synthesized gas through a recycle compressor, thence to a refrigerated chiller where the ammonia is condensed to liquid form and discharged as a finished product. The chiller may be between reactor and the recycle compressor rather than before the recycle compressor and the reactor. The latter step entails the use of a suitable refrigeration compressor and refrigeration system.
The main compressor referred to above is a highly expensive and cumbersome piece of machinery requiring not only a high initial cost of installation, but requiring also high maintenance costs and high operating costs, all of which combine to increase considerably the cost of the finished product.
Other problems associated with existing plants and processes are concerned with the high cost of power required to operate the pumping and refrigerating equipment, as well as the attendant maintenance and operational expenses.
Many steps have been taken to improve over the basic process, and the prior art as currently known to applicant is summarized briefly below.
Haber, U.S. Pat. No. 1,202,995 is the basic patent which teaches the synthesis process of ammonia.
Crooks, U.S. Pat. No. 3,054,660 teaches the use of a compressor which utilizes the expanding uncombined fraction of ammonia for its driving purposes.
Bresler, U.S. Pat. No. 2,799,562 teaches a method of controlling a high pressure compressor in an ammonia synthesis plant from the pressure in a low pressure hydrogen holder supply.
Didycz, U.S. Pat. No. 3,396,982 discloses a method of cascading catalyst beds in a reactor to improve the yield of ammonia.
Alleman, U.S. Pat. No. 3,413,091 teaches a method of recovering prematurely synthesized ammonia in a typical plant.
Yeh, U.S. Pat. No. 3,344,052 discloses the use of electrostatically charged catalysts.
Slade, U.S. Pat. No. 1,664,997 and Kniskern, U.S. Pat. No. 1,721,455 disclose respectively a method of drying ammonia by use of refrigeration below zero degrees centigrade and use of an intermediate heat exchanger for greater efficiency.
Pyzel, U.S. Pat. No. 1,849,357 discloses a method of low pressure conversion made practicable by compression of partially converted mixture, condensing, separating and using expansion for cooling and returning the ammonia.
None of the prior art presently known to applicant solves the basic problems with this process in existing plants as described above.